I bought one of the diesel heaters that is usually used in semi sleepers and i installed it in a 7x12 enclosed trailer. I had spray foamed the walls and ceiling maybe half inch thick which made a huge difference. The heater i bought is self contained with the tank and pump and heater in a metal brief case looking package. Its the 8kw version which is the largest i've seen. I have had the trailer in the mid seventies, and ive ran it for 8 or so hours and it mabe burnt a quart of fuel on the medium heat level. with the final install i used a suburban furnace vent to route the exhaust outside and i used 3 inch pvc with a sweep T closest to the funace and a 90 at the end of the pipe near the rear door. another thing i did was put hooks above the pvc pipe and drilled some half inch or so holes in the top of the pipe so if there is something on the hooks it will get warmed and or dried. I think in a larger trailer you may need two of these heaters but the install is very easy and they are only 8 inches or so wide. also when on a trip you will always be stopping at a gas/diesel station for the fuel. one more thing i believe they only draw 2 or so amps while running.
